title: Traffic-related air pollution and asthma onset in children: a prospective cohort study with individual exposure measurement.
abstract: BACKGROUND
  The question of whether air pollution contributes to asthma onset remains unresolved.
  
  
  OBJECTIVE
  In this study, we assessed the association between asthma onset in children and traffic-related air pollution.
  
  
  METHODS
  We selected a sample of 217 children from participants in the Southern California Children's Health Study, a prospective cohort designed to investigate associations between air pollution and respiratory health in children 10-18 years of age. Individual covariates and new asthma incidence (30 cases) were reported annually through questionnaires during 8 years of follow-up. Children had nitrogen dioxide monitors placed outside their home for 2 weeks in the summer and 2 weeks in the fall-winter season as a marker of traffic-related air pollution. We used multilevel Cox models to test the associations between asthma and air pollution.
  
  
  RESULTS
  In models controlling for confounders, incident asthma was positively associated with traffic pollution, with a hazard ratio (HR) of 1.29 [95% confidence interval (CI), 1.07-1.56] across the average within-community interquartile range of 6.2 ppb in annual residential NO2. Using the total interquartile range for all measurements of 28.9 ppb increased the HR to 3.25 (95% CI, 1.35-7.85).
  
  
  CONCLUSIONS
  In this cohort, markers of traffic-related air pollution were associated with the onset of asthma. The risks observed suggest that air pollution exposure contributes to new-onset asthma.
authors.affiliation: School of Public Health, Division of Environmental Health Science, University of California, Berkeley, California 94720-7360, USA. jerrett@berkeley.edu
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.forename: Ketan
authors.initials: K
authors.lastname: Shankardass
authors.forename: Kiros
authors.initials: K
authors.lastname: Berhane
authors.forename: W James
authors.initials: WJ
authors.lastname: Gauderman
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
authors.forename: Edward
authors.initials: E
authors.lastname: Avol
authors.forename: Frank
authors.initials: F
authors.lastname: Gilliland
authors.forename: Fred
authors.initials: F
authors.lastname: Lurmann
authors.forename: Jassy N
authors.initials: JN
authors.lastname: Molitor
authors.forename: John T
authors.initials: JT
authors.lastname: Molitor
authors.forename: Duncan C
authors.initials: DC
authors.lastname: Thomas
authors.forename: John
authors.initials: J
authors.lastname: Peters
authors.forename: Rob
authors.initials: R
authors.lastname: McConnell
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D000397:Air Pollution; D001249:Asthma / Q000209:etiology* / Q000503:physiopathology; D002648:Child; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D012621:Seasons; D001335:Vehicle Emissions
chemical_list: D001335:Vehicle Emissions